Semi-continuous casting equipment having a centering device for centering a bottom block relative to a casting mold

ABSTRACT

The apparatus includes an upper metal reservoir (10), a casting mold (2) having an inlet and an outlet, and a vertically moveable base (7) positioned at the outlet with a casting shoe or bottom block (5) which is designed to bear against the outlet at the start of a casting cycle. The casting shoe is mounted as a moveable shoe on the base (7) and is designed to be locked by the direct engagement with the base when it has been brought into a centered position in relation to the casting mold (2). Furthermore, centering devices (3, 4, 8) for the casting mold and the casting shoe are provided thereon for centering the casting shoe in relation to the casting mold.

BACKGROUND OF THE INVENTION

The present invention concerns direct chill, semi-continuous castingequipment for the manufacture of metal ingots. The metal used isprimarily aluminum. The casting equipment includes an upper metalreservoir, a casting mold with an inlet and an outlet, and a moveablebase positioned below the outlet with a casting shoe or bottom blockwhich is designed to bear against the outlet at the start of a castingcycle.

In connection with the manufacture of metal castings of smalldimensions, for example ingots for extrusion purposes, self-centeringcasting shoes are used. The arrangement is based on a simple principlein which the casting shoes rest on well-greased bases. The casting diesare fitted with a guide edge which guides each of the casting shoes intoplace in the dies as the moveable base is moved up. This systemfunctions satisfactorily because of the small dimensions and low weightof the casting shoes.

In connection with roll-ingot casting, however, a similar system willnot function satisfactorily because the casting shoe (just one) for thistype of casting equipment has a considerably larger bearing surface andis considerably heavier.

In connection with roll-ingot casting it is common to use manualcentering of the casting shoe by means of a bar. This results in damageto both the casting shoe and the casting mold as a consequence of thebar, and because the edge of the shoe touches the mold wall. The damagein the form of scratches and cuts on the die wall and casting shoe,respectively can result in surface defects in the roll-ingot workpiecesand, in the worst case, in leakage between the casting mold and thecasting shoe resulting in damaged workpieces.

Recently, a solution has been introduced in which the casting shoe isstationary, and the casting die or mold is centered around the shoe. Thecasting mold is thus mounted as a moveable mold and is designed to bemoved by means of eight pneumatic cylinders fitted at each of thecorners of the mold. As the pneumatic cylinders are operated manually,this solution involves the risk of the edge of the casting shoe damagingthe casting mold. In addition, such a solution employing a moveablecasting mold and a large number of pneumatic cylinders is very expensivein terms of construction and maintenance.

SUMMARY OF THE INVENTION

With the present invention, a solution to the above problems with directchill casting equipment has been developed and provides safe andaccurate centering of a casting shoe or bottom block in relation to thecasting mold, thus eliminating damage to these parts. Furthermore, thepresent invention can be manufactured at a reasonable price and issimple and inexpensive to maintain.

In accordance with the present invention the casting equipment ischaracterized in that the casting shoe is mounted as a moveable shoe onthe base and is designed so that it can be locked in relation to thebase when it has been placed in the centered position in relation to thecasting mold.

For centering the casting shoe in relation to the casting mold,corresponding centering devices are provided for the casting mold andthe casting shoe respectively.

In relation to a preferred embodiment, the support between the base andthe casting shoe can include one or more air cushions. The base and theshoe are interlocked by shutting off the air supply to the air cushionsso that the casting shoe is lowered down and rests directly on the baseafter the casting shoe has been brought into the correct position inrelation to the casting mold.

In accordance with another aspect of the preferred embodiment, thecentering devices include at least two tapered guide pins whichcorrespond to two guide sleeves connected to the casting mold or viceversa.

BRIEF DESCRIPTION OF THE INVENTION

The invention will now be described in further detail by means ofexamples and with reference to drawings in which:

FIG. 1 is a schematic illustration of casting equipment for themanufacture of roll ingots in accordance with the present invention; and

FIGS. 2-4 are similar to FIG. 1 but show the casting shoe for theequipment in different positions.

DETAILED DESCRIPTION OF THE INVENTION

Direct chill, semi-continuous casting equipment 1 for the manufacture ofroll ingots, so-called DC (direct chill) casting equipment includesgenerally, as shown in FIG. 1, an upper metal reservoir 10 which isencased by a casting mold 2, and a vertically moveable base 7 with acasting shoe or bottom block 5 which is designed to bear against theoutlet of the casting die at the start of a casting operation.

Devices for water chilling of the metal during the casting operation,possibly devices for the supply of gas or lubricant to the casting mold,and devices for vertical movement of the base are not shown in thedrawing as they do not form part of the invention and are unnecessaryfor an understanding of it.

As mentioned, the casting shoe or bottom block 5 bears against thecasting mold outlet and forms the base of the outlet at the start of acasting operation. Liquid metal is supplied to the reservoir 10 fromabove, and as soon as the metal beings to harden at the casting shoe 5,the shoe is lowered downwardly together with the base 7. At the sametime water is supplied through a slot (not shown) which chills the metalfurther so that a long metal workpiece is formed with a cross-sectionwhich is defined by the opening in the casting mold 2. When the base 7has reached its lowermost position, the casting operation stops, thecast metal workpiece is removed, and the base 7 with the casting shoe 5is moved back to its original position for commencement of a new castingoperation.

The special feature of the present invention is that a support and acentering device (3, 4, 6) are fitted between the base 7 and the castingshoe 5 which makes it possible to center the casting shoe securely andin an accurate position in relation to the casting mold. In the exampleshown in the drawings the support includes air cushions 6 fitted betweenthe casting shoe 5 and the base 7. The air cushions 6 can be locatedadequately in recesses 9 formed in the casting shoe 5 or the base 7 sothat they are located completely in these recesses and so that thecasting shoe rests directly (metal against metal) on the base when theair supply is shut off.

The centering device includes at least two (one at either end of thecasting shoe) guide pins 3 protruding downwardly from the casting mold2. The guide pins 3 are designed to correspond to guide sleeves oropenings on the casting shoe 5. The positions of the pins 3 and thesleeves 4 may be reversed. Both the pins 3 and the sleeves 4 haveconically shaped surfaces 13, 14 which guide the two parts into aninterfitting position with each other. Each guide sleeve 4 is fitted indetachable and adjustable juts or brackets 8 so that they can beadjusted individually in advance in relation to the particular castingshoe to ensure that the casting shoe is in the correct position duringthe centering operation. Instead of pins and sleeves, another centeringdevice may be used, if required, for example wedges with bevel edgespointing downwards from the casting mold which bear against the outsideof the casting shoe 5. The casting shoe 5 is, moreover, fitted with adownwardly projecting edge 11 which prevents it from being displaced toofar sideways in relation to the base 7, and thus ensures that the guidepins 3 are inserted into the sleeve 4.

In connection with the process of centering the casting shoe 5 into thecorrect position before a casting operation, the base 7 is movedupwardly, and air or another gas is supplied (not shown in furtherdetail) to the air cushions 6. The casting shoe 5 will consequently moveupwardly and out of the friction interlock or engagement with the base,as shown in FIG. 2. The casting shoe can thus easily be moved sideways,and the impact on the guide pins 3 and the guide sleeves 4 will beminimal.

The centering operation can now be performed by raising the base 7 to anupper level at which the upper part of the casting shoe 5 is inside ofand slightly protruding from the lower edge of the casting mold 2 asshown in FIG. 3. The air or gas supply is subsequently shut off so thatthe casting shoe 5 sinks down a few millimeters and again interlocksfrictionally with the base 7 as shown in FIG. 4. It is important thatthe casting shoe 5 is not displaced in relation to the base 7 during thecasting operation as such displacement would result in the castingworkpiece being destroyed. Frictional locking, i.e. when the castingshoe rests directly on the base, will probably be sufficient for mostcasting molds to keep the casting shoe in place. As an extra measure,however, an extra locking device, such as a clamp device which pressesthe casting shoe against the base, can be provided.

The whole centering operation can be performed automatically by means ofa logic control guide unit and electrical switching devices andcomponents which are generally known, and therefore will not bementioned further here.

In the example shown in the figures and described above, it has beenindicated that the support between the casting shoe and the baseincludes two air cushions 6. It should be noted that the invention asdefined in the claims is not limited to two cushions but can be usedwith one cushion or more than two cushions. Moreover, the invention isnot limited to the use of cushions. Thus, for example, a ball supportcan be used which can be raised mechanically in order to lift thecasting shoe from the base during the centering operation. Also, othertypes of support may possibly be used, but the necessary condition forthis is that they result in so little friction that the casting shoe caneasily be moved on the base.

We claim:
 1. A direct chill casting apparatus comprising:a casting moldhaving an inlet, an outlet, and defining a casting area between saidinlet and said outlet; a vertically moveable base movably mounted forvertical movement relative to said casting mold between a start positionand a lowered position located below said start position; a bottom blocksupported by said moveable base for movement with said moveable basebetween a first position in which said bottom block bears against saidoutlet and a second position below said first position; and a bottomblock centering device including at least one air cushion positionedbetween said moveable base and said bottom block and being adjustablebetween an inflated state in which said at least one air cushionsupports said bottom block above said moveable base and allows lateralmovement of said bottom block relative to said moveable base, and adeflated state in which said bottom block rests on and frictionallyengages said moveable base.
 2. The direct chill casting apparatus asclaimed in claim 1, wherein said at least one air cushion comprises twoair cushions.
 3. The direct chill casting apparatus as claimed in claim1, wherein said centering device further comprises:at least two taperedguide pins connected to said casting mold; and at least two sleevesconnected to said bottom block, said at least two sleeves havingconically shaped openings for guiding said at least two tapered guidepins into said at least two sleeves, respectively.
 4. The direct chillcasting apparatus as claimed in claim 3, further comprising two bracketsmounted on said bottom block, wherein said at least two sleeves aresupported on said bottom block by said at least two brackets,respectively.
 5. The direct chill casting apparatus as claimed in claim1, wherein said bottom block includes a lower surface which opposes anupper surface of said moveable base, and said bottom block has aprojection which is positioned outwardly of said moveable base andextends downwardly below said upper surface of said moveable base.
 6. Adirect chill casting apparatus comprising:a casting mold having aninlet, an outlet, and defining a casting area between said inlet andsaid outlet; a vertically moveable base movably mounted for verticalmovement below said casting mold outlet; a bottom block supported onsaid moveable base and having a first surface opposing said outlet ofsaid casting mold, and a second surface opposing said moveable base andlocated opposite said first surface, wherein said second surface has atleast one recess defined therein; and a bottom block centering devicefor centering said bottom block relative to said casting mold, saidcentering device including at least one air cushion positioned in saidat least one recess.
 7. The direct chill casting apparatus as claimed inclaim 6, wherein said at least one air cushion comprises two aircushions, and said at least one recess comprises two recesses.
 8. Thedirect chill casting apparatus as claimed in claim 6, wherein saidcentering device further comprises:at least two tapered guide pinsconnected to said casting mold; and at least two sleeves connected tosaid bottom block, said at least two sleeves having conically shapedopenings for guiding said at least two tapered guide pins into said atleast two sleeves, respectively.
 9. The direct chill casting apparatusas claimed in claim 8, further comprising at least two brackets mountedon said bottom block, wherein said at least two sleeves are supported onsaid bottom block by said at least two brackets, respectively.
 10. Thedirect chill casting apparatus as claimed in claim 6, wherein saidbottom block includes a lower surface which opposes an upper surface ofsaid moveable base, and said bottom block has a projection which ispositioned outwardly of said moveable base and extends downwardly belowsaid upper surface of said moveable base.